Morton (0-3, 4.35) has lost his last three starts, including a 5-2 setback against the Cincinnati Reds last Wednesday. He walked a season-high five batters in the setback while allowing four runs -- three earned -- and four hits in six innings.
Morton will face fellow right-hander Chris Tillman (3-1, 3.38 ERA) on Wednesday. The Pirates originally had righty Brandon Cumpton (0-1, 2.57) set to start the second game of the series against Bud Norris (1-2, 4.44).
"At the end of the day, the game takes care of those who take care of the game," manager Clint Hurdle said pregame about his struggling squad. "If you're not taking care of the game, it's hard to win. We've got to do a better job of taking care of the game and meeting those demands."
Baltimore has won three of its last five games. The Orioles are expected to activate third baseman Manny Machado from the disabled list. The rising star has not played a Major League game this season after undergoing knee surgery last September.
Last season, Pittsburgh finished with a MLB-best 15-5 record in Interleague Play.
Tickets for Tuesday's game will be honored for Thursday's game, the Orioles announced.